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<title>OMP_NUM_THREADS (GNU libgomp)</title>

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Next: <a href="OMP_005fPROC_005fBIND.html" accesskey="n" rel="next"><code class="env">OMP_PROC_BIND</code> &ndash; Whether threads may be moved between CPUs</a>, Previous: <a href="OMP_005fNUM_005fTEAMS.html" accesskey="p" rel="prev"><code class="env">OMP_NUM_TEAMS</code> &ndash; Specifies the number of teams to use by teams region</a>, Up: <a href="Environment-Variables.html" accesskey="u" rel="up">OpenMP Environment Variables</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Library-Index.html" title="Index" rel="index">Index</a>]</p>
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<h3 class="section" id="OMP_005fNUM_005fTHREADS-_002d_002d-Specifies-the-number-of-threads-to-use"><span>4.9 <code class="env">OMP_NUM_THREADS</code> &ndash; Specifies the number of threads to use<a class="copiable-link" href="#OMP_005fNUM_005fTHREADS-_002d_002d-Specifies-the-number-of-threads-to-use"> &para;</a></span></h3>
<a class="index-entry-id" id="index-Environment-Variable-8"></a>
<a class="index-entry-id" id="index-Implementation-specific-setting-1"></a>
<dl class="table">
<dt><em class="emph">Description</em>:</dt>
<dd><p>Specifies the default number of threads to use in parallel regions.  The 
value of this variable shall be a comma-separated list of positive integers;
the value specifies the number of threads to use for the corresponding nested
level.  Specifying more than one item in the list will automatically enable
nesting by default.  If undefined one thread per CPU is used.
</p>
</dd>
<dt><em class="emph">See also</em>:</dt>
<dd><p><a class="ref" href="omp_005fset_005fnum_005fthreads.html"><code class="code">omp_set_num_threads</code> &ndash; Set upper team size limit</a>, <a class="ref" href="OMP_005fNESTED.html"><code class="env">OMP_NESTED</code> &ndash; Nested parallel regions</a>
</p>
</dd>
<dt><em class="emph">Reference</em>:</dt>
<dd><p><a class="uref" href="https://www.openmp.org">OpenMP specification v4.5</a>, Section 4.2
</p></dd>
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